dhb.4

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)dhb.4	2.4	2/29/88
.TH dhb 4
.SH Name
dhb \- DHB32 communications multiplexer
.SH Syntax
.B "device dmb0 at vaxbi? node? flags 0x????"
.br
.ti +0.5i
.B "vector dmbsint dmbaint dmblint"
.SH Description
.NXR "DHB32 communications interface"
.NXS "dhb interface" "DHB32 communications interface"
A
DHB32
device provides 16 asynchronous
communication lines with full modem control.
The DHB32 and the DMB32 share a common software device driver.
For this reason, the configuration line is the same for both
the DHB32 and DMB32.
.PP
Each line attached to a
DHB32
serial line port behaves as described
in
.MS tty 4 .
Input and output for each line can independently be set to run at any
of 16 speeds.  See
.MS tty 4
for the encoding.
.PP
Bit
.I i
of flags may be specified for a
.PN dhb
to say that a line 
should be treated as a hardwired connection with carrier always present.
If bit
.I i
of flags is not set, the line will operate under full modem control.
Modem lines will operate in accordance to the CD (carrier detect),
DSR (data set ready) and CTS (clear to send) leads.
Thus, specifying ``flags 0x0004'' in the specification of
.PN dmb0
would cause line 2 on the DHB32 to be treated as hardwired
with carrier always present.
In this example, the remainder of the lines will be modem control lines.
.SH Diagnostics
.B "dmbinit: async lines unavailable"
.br 
This message is produced at system boot time if the DHB32
fails its internal self test indicating that the asynchronous lines have
failed to configure.
.PP
.B "dmb%d: fifo overflow" 
.br
The character input fifo overflowed
before it could be serviced.  This can happen if the CPU is running
with elevated priority for too long a period of time.  Overflow errors may
indicate that configuration constraints have been reached.
.PP
.B "dmb%d: DMA Error. tbuf = 0x%x"
.br 
A DMA output transfer failed.  This problem can result from a memory error
or an invalid pte (page table entry).
For a description of the error code in the
``tbuf'' register. See the DHB32 documentation.
.PP
.B "dmb%d: DMB Hardware Error. TX.DMA.START failed"
.br 
The 
.PN dhb 
failed to clear the start bit.  Normally, this is cleared to signal
that a DMA transfer has completed.
.PP
.B "dmb%d: Modem Error. tbuf = 0x%x"
.br 
Indicates a problem with a modem or its cable.
For a description of the error code in the
``tbuf'' register. See the DHB32 documentation.
.PP
.B "dmb%d: Internal Error. tbuf = 0x%x"
.br 
Indicates that the DHB32 detected an internal error.
For a description of the error code in the
``tbuf'' register. See the 
.I "DHB32 User Guide."
.SH Files
.TP 15
.PN /dev/tty??
.TP
.PN /dev/ttyd?
(modem lines only)
.SH See Also
tty(4), MAKEDEV(8), dmbsp(4)